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18 Cards in this Set

  • Front
  • Back
=energy of motion of atoms/molecules of an object

absolute zero=temp at which all motion ceases. (0 K, -273 C, -459 F)
legnth over which wave repeats in pattern (meters)
how often the wave repeats itself (cycles per second)
wavelegnth times frequency
electromagnetic spectrum
radio, infrared, visible, ultraviolet, x-ray, gamma ray

(left to right) frequency increases, wavelegnth decreases
the hotter the object..
-> higher temp -> faster the particles move -> more energy they radiate
(more intensely it radiates energy)
blackbody curve
=distribution of reemitted radiation; in steady state, (when T is contant), blackbody must reemit same amount of energy it absorbs

curve shifts toward higher frequencies (shorter wavelegnths) and greater intensities as the object's temp increases
stefan-boltzmann law
intensity of light is directly related to temp of the object to the fourth power

intensity= T^4
wien's law
wavelegnth of peak emission= 1/T
the hotter an object, the bluer its radiation/ the shorter its wavelegnth
continuous spectra
covers full range of wavelegnths
rainbow running from red to violet w/out interruption.
emission spectra
pattern of spectral emission lines that represent emission at only certain wavelengths

hot,low density gas
absorption spectra
certain wavelegnths missing; dar lines in otherwise continuous bright spectrum, where light w/in 1 narrow frequency range has been removed

cool, low density gas
model of atom
protons=positive; # determines what element it is
neutrons=neutral; # determines what isotope the element is
electrons=negative; orbit the nucleus
why movement of electrons around nucleus cause atom to absorb/emit enegery?
1.opposites attract
2.discrete levels; different electrons have different allowed electron levels. closest are in ground state
3.discrete energy levels
4.when electron absorbs enough energy, can pull away- ion
energy levels
if low energy photon strikes electron, it is absorbed and electron jumps up 1 level

higher energy photon will cause electron to jump 2 levels

higher energy of photon=higher jump

electron in higher levels= excited (but wants to go back into ground state)
hydrogen spectra
hydrogen= most abundant element in universe; simplest atom

lyman series:91-122 nm (UV)
balmer series:365-656 nm (visible and UV)
paschen series:820-1875 nm (IR)
doppler effect
observer in front of source: shorter wavelegnths, blueshifted
observer in back of source: longer wavelegnths, redshifted
blueshift: shift towards blue (shorter wavelegnths)due to object moving towards us

redshift: shift towards red end of spectrum (longer wavelengths)